The present invention relates to a wide-voltage-range converter.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
An electric motor having a predetermined motor voltage can be connected to different power supplies. The power supplies differ from one another in terms of their power supply voltages. The essential power supply voltages of a three-phase power supply are 200 V to 240 V, 380 V to 480 V, 500 V to 600 V and 660 V to 690 V. A converter is required for operation of the motor, with the converter being connected between a feed power supply and the motor.
A converter of this type has a converter unit on the power supply side and on the load side, these converter units being linked to one another on the DC voltage side. A self-commutated pulse-controlled converter unit is predominantly used as the load-side converter unit. Various converter units can be used on the power supply side. A commercially available simple converter, also referred to as a frequency converter, has a diode bridge as the power-supply-side converter unit. This uncontrolled power-supply-side converter unit is connected to the DC-voltage-side connections of the self-commutated pulse-controlled converter unit on the DC voltage side by means of a voltage intermediate circuit having at least one capacitor.
If energy is to be fed back into the feeding network, then a diode rectifier is used, a respective turn-off semiconductor switch being electrically connected antiparallel with respect to the diodes of the rectifier. The turn-off semiconductor switches are in each case turned on during the current conduction times of the associated diodes, which are determined by the natural commutation instants. On the power supply side, this converter unit controlled at the power supply frequency has a filter having three star- or delta-connected capacitors. The voltage intermediate circuit, which connects the power-supply-side converter unit to the load-side converter unit on the DC voltage side has no capacitors in the case of this converter topology. As a result of the configuration of the power-supply-side converter unit, which is also referred to as the fundamental frequency front end (F3E), this converter is regenerative.
In the case of a further converter topology, instead of a diode rectifier, a self-commutated pulse-controlled converter unit having an inductor in each of the supply lines on the AC voltage side is used as the power-supply-side converter unit. On the DC voltage side, the power-supply-side converter unit, which is also referred to as the active front end (AFE), is electrically conductively connected to the DC-voltage-side connections of the load-side converter unit, in particular of a self-commutated pulse-controlled converter unit, by means of a voltage intermediate circuit having at least one capacitor, preferably an electrolytic capacitor. The use of an AFE as the power-supply-side converter unit means that this converter is congenial to the power supply and regenerative. Moreover, an intermediate circuit voltage is regulated to a predetermined value in a constant fashion.
In the case of a conventional wide-voltage-range converter whose power-supply-side converter unit is embodied in one of the aforementioned topologies (diode rectifier, F3E, AFE), it is necessary to accept a pronounced power derating or else a relatively high power loss. For these reasons, a converter is chosen which, on the power supply voltage side, is adapted to the power supply voltage of a feed power supply and, on the load side, is adapted to a power requirement of a motor to be driven having a predetermined motor voltage.
It would therefore be desirable to provide a wide-voltage-range converter which does not exhibit power derating during operation and which can contactless transmit power between a power-supply-side converter unit and a plurality of load-side converter units.